Can The Outdoor AC Unit Be Set Higher Than The Indoor Unit?

Charlie D Paige profile pic

An outdoor AC unit’s most common installation location is on a ground-level concrete pad. If this installation arrangement is not feasible for your structure, can the outdoor AC be installed higher than the indoor unit?

The outdoor AC unit can be set or installed higher than the indoor unit. The outdoor AC can be installed on the roof of a building provided the roof is flat and accessible, or it can be mounted on an outside wall above the indoor AC unit. The unit must be accessible for servicing and maintenance.

Should the possibility of installing an outdoor AC above the height of the indoor unit be possible, are there any limitations to the distance or any potential problems with this installation arrangement? We will discuss these possibilities and any limitations your should bear in mind for this situation.

Can An Outdoor AC Be Installed Higher Than The Indoor AC?

An AC compressor unit
An AC compressor unit

It is not only possible for the outdoor unit of a split AC unit to be installed at a higher elevation than the indoor unit, but in some cases, it is a desirable configuration for several reasons.

One of the main reasons people consider this arrangement is when the room where the AC will be installed is high above the ground, or boundary walls cannot accommodate a ground floor installation.

What are the alternative options and various considerations for the installation of the outdoor unit in these circumstances?

It is possible to install the compressor or outdoor AC unit at a height greater than the indoor unit, and in some cases, it is more desirable. The compressor can be a noisy component of the outdoor AC unit, creating undesirable noise pollution if installed at ground level.

This is particularly the case if the only space for the outdoor AC is outside a window. The noise of the compressor can become an irritation to the occupants of the building.

Can The Outdoor AC Be Installed On A Roof?

Roof mounted AC compressor air con units
Roof mounted AC compressor air con units

An outdoor AC unit can be installed on the roof of a building as an alternative position to a ground floor pad. This configuration can benefit the AC unit as well as solve some issues of the occupants of the building.

There are some considerations for installing the outdoor AC on the roof, which must be given attention to ensure the system will function correctly.

  • The roof must be flat. It is important that an AC compressor is installed level. This requires a flat surface to mount the outdoor unit and retain a perfect level. Tilt in the compressor installation can result in poor functioning of the unit.
  • Distance from the indoor unit. Most AC manufacturers limit the distance the outdoor unit can be from the indoor unit, especially when the distance relates to height.
  • Keep the pipes straight. The pipes between the two units must be as straight as possible. Bends in the pipe can affect refrigerant and lubricant flow in the system.
  • Adequate vibration dampening. A roof installation of the outdoor AC unit must include vibration dampening to prevent noise from being transmitted through the roof.
  • Accessibility for maintenance. The outdoor unit will require maintenance and servicing by an HVAC technician. The unit must be easily accessible for these maintenance checks, or the technician can refuse the job or charge extra for the inconvenience.

Besides the installation considerations, a roof installation of the compressor can have a number of benefits. The noise of the compressor fan is reduced when the unit is installed on the roof. This makes the AC more silent for the occupants of the building, provided that proper vibration dampening has been installed.

In some buildings, such as apartment buildings, it is preferred to install outdoor AC units on the roof of the building. This helps with airflow around the compressor and makes the units more accessible for servicing

Buildings with a pitched roof are generally unsuitable for installing the outdoor AC on the roof. The angle of the pitch does not accommodate the level installation of the compressor unit without modifying the roof structure.

Installing the outdoor AC unit higher than the indoor unit can benefit the efficiency of the unit. The refrigerant will not need to be pumped upwards against gravity but rather down with gravity, reducing workload for the outdoor unit pump.

Can An Outdoor AC Be Installed On The Wall Above The Indoor Unit?

An outdoor wall mounted AC compressor air con unit
An outdoor wall mounted AC compressor air con unit

In some instances, installation on the ground or on the roof are not viable installation options. In this circumstance, it is possible to install the unit on a bracket mounted to the wall of the building. 

When the outdoor AC unit is installed on a wall, it is possible to install the outdoor unit above the indoor unit. This reduces the distance between the two units and would be the most logical choice in many cases.

There are some considerations to installing the outdoor unit above the indoor unit on a wall, but if these are taken into account, it can be a suitable and successful location.

  • Accessibility of the outdoor AC for servicing. The height of the AC unit above the ground, or a firm surface such as a balcony or terrace, should be such that it is easily accessible by the service technician. If the unit position makes access difficult or dangerous, additional costs may be incurred for services and maintenance. It is not easy servicing an AC compressor while balancing on a ladder!
  • Distance from the wall. The minimum distance an outdoor unit can be installed from a wall is typically 2 feet. This is to promote sufficient airflow around the unit for cooling. The wall bracket must extend at least this distance from the wall to provide airflow space.
  • Secure mounting. AC compressors are heavy pieces of equipment. The construction of the wall must be robust enough to accommodate the weight of the outdoor AC unit.
  • Vibration dampening. The compressor in the outdoor AC unit can cause vibrations which can be transmitted through the wall-mounted bracket into the wall. This means sufficient vibration dampening must be used where the AC unit is mounted to the bracket. 

When mounting the outside AC to a wall, the exhaust location of the unit should be taken into account. If the exhaust is near a window or a door, such as a balcony door, it can heat up the room’s interior. The compressor exhaust expels hot air that it has extracted from the refrigerant, and this hot air blasting against a window or entering a doorway can adversely influence the interior temperature.

So long as these aspects are taken into account, a wall mount can be an excellent location for the outdoor unit, whether above below, at the same level as the indoor unit. This is an advantage because it limits the distance between the two units. Less distance means shorter pipes reducing the potential for leaks and less distance for the refrigerant and lubricant to travel.

Height Installation Limitations For An Outdoor AC

Even though it is permissible for the outdoor AC unit to be installed above the indoor unit, there are some limitations to the height before certain adjustments must be made.

Most AC manufacturers stipulate that the outdoor unit should not have a vertical distance of more than 16 feet or 5 meters.

If this distance limit is to be exceeded, adjustments need to be made to the amount of refrigerant in the pipes. The longer the pipes, the more refrigerant is needed to keep them filled.

The distance can be extended to a vertical separation of 65 feet or 20 meters with the addition of more refrigerant to the system. A distance of 98 feet or 30 meters should not be exceeded to maintain the efficiency of the system

The amount of additional refrigerant that must be added to the system will vary from system to system, depending on the length and diameter of the pipes. The manufacturer documentation will give the refrigerant volume to add per extra foot of distance.


An outdoor AC unit can be installed higher than the level of the indoor AC unit. There are some vertical distance restrictions, which require additional refrigerant added to the system if they are exceeded.

In many cases, installing the outdoor unit higher than the indoor unit is advantageous for noise suppression, aesthetics, and practical reasons. If you need to install the outdoor AC unit in a position other than a concrete pad on the ground, it is best to consult with an expert.

Charlie D Paige profile pic
About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.